1. Field of the Invention
The present invention pertains to a modular compliance monitoring apparatus for use with a conventional pressure support system that monitors whether a patient is complying with a prescribed pressure support therapy delivered by that system.
2. Description of the Related Art
Patients suffering from a pulmonary or respiratory disorder, such as obstructive sleep apnea (OSA), are often prescribed a pressure support therapy that is provided by a pressure support device, such as a continuous positive airway pressure (CPAP) device. A CPAP device delivers a flow of fluid to the airway of the patient throughout the patient's breathing cycle in order to “splint” the airway, thereby preventing its collapse during sleep. It is also known to provide a bi-level positive pressure therapy, in which the pressure of fluid delivered to the patient's airway varies or is synchronized with the patient's breathing cycle to maximize the medical effect and comfort to the patient. In a “bi-level” pressure support system, the patient receives an inspiratory positive airway pressure (IPAP) during inspiration that is greater than an expiratory positive airway pressure delivered (EPAP) during expiration.
It is further known to provide an auto-titration positive pressure therapy in which the pressure provided to the patient changes based on the detected conditions of the patient, such as whether the patient is snoring or experiencing an apnea, hypopnea, or upper airway resistance. Still other modes of providing a pressure support therapy are know, such as proportional positive airway pressure (PPAP), as taught, for example, in U.S. Pat. Nos. 5,535,738; 5,794,615; and 6,105,575 all Estes et al. and proportional assist ventilation (PAV), as taught, for example, in U.S. Pat. Nos. 5,044,362 and 5,107,830 both to Younes et al.
In treating a patient using any of the above-described pressure support systems or modes of pressure support, it is often desirable to monitor various parameters associated with the use of such systems. For example, the patient's healthcare provider, such as that patient's physician or health insurance company, is interested in ensuring that the patient actually uses the pressure support therapy as prescribed. Thus, it is known to monitor a patient's compliance with the prescribed therapy by monitoring the patient's usage of the pressure support device.
Typically, a doctor or other health care provider tracks a patient's compliance with the prescribed pressure support therapy by tracking the operation of the prescribed pressure support device. For example, U.S. Pat. Nos. 5,715,812 and 5,517,983 both to Deighan et al. teach a pressure support system that includes a built-in status monitor that determines the usage of the pressure support system by the patient. The status monitor includes a sensor, such as pressure sensor, motor current sensor, temperature sensor, or valve position sensor, that detects patient respiration and a timer that is actuated by the sensor. The timer accumulates the time of usage of the pressure support system by the patient based on the output of the sensor.
One disadvantage of the compliance monitoring system taught by these patents is the components of the compliance monitor are built-in to the pressure support system. As a result, it is not possible to readily remove or exclude the expensive components required for compliance monitoring for pressure support systems that do not require compliance monitoring.
U.S. Pat. No. 5,706,801 to Remes et al. teaches a stand-alone monitor for use with an oxygen concentrator. This monitor is not intended for use with a pressure support system that delivers a flow of gas according to prescribed modes of pressure support. The monitoring device taught by the '801 patent monitors the patient's usage of the oxygen concentrator by sensing the flow of oxygen through the monitor. At the time oxygen enriched air is detected to be flowing through the monitor, it records that time as the start of the oxygen therapy session. Conversely, when oxygen enriched air ceases flowing through the monitor, it records that time as the end of the session.
However, the monitor of the '801 patent is not capable of determining whether a patient is actually breathing into the cannula through which the oxygen flows. That is, if the oxygen concentrator is turned on and left running without the cannula being connected to the patient, the monitor taught by the '801 patent would record this as a valid session even though the oxygen is not being delivered to the patient. Thus, the monitor taught by the '801 patent is easily fooled into recording a valid session so long as the oxygen concentrator is running and providing a flow of gas through the monitor regardless of whether the patient is actually receiving the oxygen from the cannula.